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PROPOSED DRILL SITES

Primary Sites

Site BT4-2A

Primary proposed Site BT4-2A is located in the center of the Brazos-Trinity Basin #4 (Fig. F7). The site has 155 m of basinal turbidites underlain by 110 m of hemipelagic drape. Hole A will be drilled and cored to 340 mbsf with APC drilling with drillover. Extended core barrel (XCB) coring will be used if APC refusal is reached before 340 mbsf. Hole A will include three APC temperature (APCT) and one Davis-Villinger Temperature-Pressure Probe (DVTPP) temperature measurements and two temperature/dual pressure probe (T2P) deployments and will be the wireline logging/vertical seismic profile (VSP) hole. Hole A will be filled with heavy mud after operations. Site BT4-2A Hole B will be the dedicated MWD hole. Hole B will be offset 20 m from Hole A.

Site BT4-4A

Primary proposed Site BT4-4A is near the southern termination of Brazos-Trinity Basin #4 (Fig. F7). The site has a thin veneer of basin fill sediments (23 m) that is underlain by 128 m of hemipelagic mudstone. Site BT4-4A Hole A will be drilled and cored to 230 mbsf. APC drilling with drillover to refusal will be used. XCB coring will be used if APC operations do not reach 230 mbsf. Hole A will include three APCT and one DVTPP temperature measurements and two T2P deployments and will be used for wireline logging and VSP if time is available. Heavy mud will be used to fill Hole A. Hole B, the dedicated MWD hole, will be offset 20 m from Hole A.

Site URS-1B

Primary proposed Site URS-1B has the shallowest water depth (1057 m water depth) and the deepest penetration (612 mbsf) (Fig. F10). The anticipated lithology is hemipelagic mud. Interbedded levee sands may be encountered below 481 mbsf. A total depth of 612 mbsf completes drilling and operations 20 m above the top of the Blue Unit (632 mbsf). Hole A will be used for MWD measurements to include PWD (safety panel requirement). Hole B will be the drilling and coring hole, completed with APC drilling with drillover; XCB will be used if APC refusal occurs above 612 mbsf. Three APCT and one DVTPP temperature measurements will be made in the hole. Heavy mud will be used for coring from 481 to 612 mbsf to minimize risk of flow from levee sands. Wireline logging and VSP will be completed in Hole B. Site URS-1B Hole C will be used for five T2P deployments. APC half-cores will be collected before each T2P deployment. No additional coring is planned for Hole C. The hole will be filled with heavy mud. The offset between the holes will be about 20 m in a direction away from any channel fill.

Site URS-2C

The hemipelagic mudstones and levee sands at primary proposed Site URS-2C are 378 m thick above the Blue Unit (Fig. F10). We will drill to 358 mbsf, 20 m above the Blue Unit. Hole A will be used for MWD measurements including PWD (safety panel requirement). Hole B will be cored with APC drilling with drillover; XCB will be used if APC refusal occurs above 358 mbsf. Three APCT and one DVTPP temperature measurements will be made in the hole. Heavy mud will be used for coring from 328 to 358 mbsf to minimize the risk of sand flow from the levee sands. Wireline logging and VSP will be completed in Hole B if time is available. Site URS-1B Hole C will be used for five T2P deployments. APC half-cores will be collected immediately before each T2P deployment. No other coring is planned for Hole C. The offset between the holes will be about 20 m in a direction away from any channels.

Site URS-3C

Primary proposed Site URS-3C is located where the hemipelagic mud is thin (258 m) (Fig. F10). The drilling plan will penetrate to 238 mbsf to prevent any communication with the Blue Unit. Hole A will be used for MWD measurements. We will core Hole B with APC drilling with drillover; XCB will be used if APC refusal occurs above 238 mbsf. Three APCT and one DVTPP temperature measurements will be made in the hole. One deployment of the T2P will be made in Hole B. At 238 mbsf, the hole will be filled with heavy mud. The offset between the holes will be about 20 m. No wireline logging is planned at Site URS-3C.

Alternate Sites

Site BT4-1B

Alternate proposed Site BT4-1B is on the northern flank of the Brazos-Trinity Basin #4 where basin-filling turbidites overlie hemipelagic mudstone (Fig. F7). A drilling depth of 300 mbsf is proposed for this site in 1405 m of water. Hole B will be for MWD operations. Hole A will employ APC drilling with drillover and will include three APCT and one DVTPP temperature measurements. Two T2P deployments will occur in Hole B. Hole A and Hole B will be offset by 20 m.

Site BT4-3A

Alternate proposed Site BT4-3A is located on the southern flank of the Brazos-Trinity Basin #4 (Fig. F7) within a thin section of basin turbidites (87 m) that is underlain by a thicker section of hemipelagic mud (115 m). The site will be drilled through the hemipelagic drape to 280 mbsf. Hole B will be for MWD operations. Hole A will employ APC drilling with drillover and include three APCT and one DVTPP temperature measurements. Two T2P deployments are planned for Hole B. Hole A and Hole B will be offset by 20 m.

Site URS-4A

Alternate proposed Site URS-4A is similar to Site URS-3C with thin hemipelagic mudstone (257 m) above the Blue Unit, and overpressures are expected (Fig. F10). Drilling, coring, logging, and measurement operations are identical to those designed for Site URS-3C with a shift in total depth to 237 mbsf to allow 20 m between the base of the hole and the top of the Blue Unit (257 mbsf).

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